Machined sidewalls...
 

I've been looking at buying a pair of black DP18 wheels off of ebay, the only thing really stopping me is that I plan on using a front brake for the time being, and none of them have machined sidewalls. How big of a difference do machined sidewalls make vs. non-machined ones? Will I be alright using brakes on the non-machined ones?

brakes can be used on non-machined rims, but performance will suffer and the braking surface will begin to look worn/inconsistent.

There will be a slight loss of braking power when dry and a pretty dramatic loss if the surface is wet compared to machined rims.

If you like stopping on rainy streets, get something machined.

some people will say there is almost no difference in braking power. i'm not so sure those people are correct. is the brake going to be your primary stopping method? if it is then i would try to find some machined rims. i have a brake on nonmachined rims but i rely on resisting for most of my slowing/stopping. the only time i really notice any disadvantage to having nonmachined rims is when it is wet, you can still stop but your brakes will squeak like crazy.

I was just planning on using the front brake in emergencies, and resisting/skidding the other 98% of the time.

that's what i do, and i've been fine. i did recently run into a guy, but that was his fault and because i didn't have the time to even get my hand to the brake, not because the brake failed.

You could always take a sanding block and machine them yourself...

^^^ do that and post pictures.

Gimme some unmachined deep-v's and I'll do just that.